1. Field of the Invention
The present invention relates to a press type mechanical pencil, more particularly to a press type mechanical pencil having a cartridge type refill tube, and to a cartridge type refill tube for use in a press type mechanical pencil.
2. Description of Related Art
There are available on the market traditional pencils having a piece of graphite enclosed in a wooden cylinder, no-sharpening pencils, and mechanical pencils.
In use, traditional pencils need to be sharpened with the use of a pencil sharpener or a cutter. No-sharpening pencils are pencils having a plurality of sharpened graphite pieces fixed in plastic units stored in a cylinder of plastic. In use, when one of the graphite pieces has become blunt due to writing, it is removed from a rear end of the cylinder and inserted into a top end of the cylinder to allow the graphite piece now at the rear end to extend out of the cylinder for writing purposes. Both of these two types of pencils cannot be used after a period of time since the graphite pieces will be used up. Besides, traditional wood pencils have to be sharpened from time to time.
Mechanical pencils are developed to improve the drawbacks of the above-mentioned pencils. A conventional mechanical pencil includes a barrel containing a hollow refill storing tube, an upper end thereof being connected to a press portion. When the press portion is depressed, a spring of a clamp/release portion below the refill storing tube is compressed so that clamp pawls at an end portion thereof open to allow passage of an elongate refill through the clamp/release portion and extension thereof from a tapered portion at the bottom portion of the barrel for writing purposes. An advantage of mechanical pencils is that the refills have a certain diameter, the width of the lines written can be consistent. Besides, the refills are refillable.
In use, with mechanical pencils, the refills have to be pre-stored in a hollow refill storing tube. When a refill is used up, the press portion is taken down to allow replacement of a new refill. As the refill has a very small diameter, it may easily break if not handled with care. In addition, the user has to touch the refill, which may stain the user's fingers. Furthermore, conventional refill storing tubes are usually small and cannot contain too many refills to reduce the frequency of refilling. These are problems to be overcome in the art.